Gemini surfactants (sometimes called dimeric surfactants) have two hydrophilic groups and two hydrophobic groups in the molecules, in contrast to conventional surfactants that generally have a single hydrophilic group and a single hydrophobic group in the molecule. Gemini surfactants can be ten to a thousand times more surface-active than conventional surfactants with similar but single, hydrophilic and hydrophobic groups in the molecules.